Cu-fe system alloy

ABSTRACT

A HIGHLY CORROSION-RESISTANT ALLOY OF THE SYSTEM CU-FE, WHICH HAS BOTH COPPER-ALLOY LIKE CHARACTERISTICS IN PRODUCTION TECHNIQUES AND CORROSION-RESISTANT PROPERTIES, AND STEEL-LIKE CHARACTERISTICS IN STRENGTH AND LOW COST, THE ALLOY CONSISTING OF 2-50 WEIGHT PERCENT CU, 5-20 WEIGHT PERCENT NI, 15-35 WEIGHT OF MN, AND THE BALANCE OF FE, WITH 0.01-15 WEIGHT PERCENT CR OR 0.01-5 WEIGHT PERCENT AL ADDED THERETO.

United States Patent 3,740,211 Cu-Fe SYSTEM ALLOY Syoji Ueda, Kazuhiko Muto, and Shintaro Matsuo, Nagasaki, Japan, assiguors to Mitsubishi Jukogyo Kabushilki Kaisha, Tokyo, Japan No Drawing. Continuation-impart of abandoned application Ser. No. 805,367, Mar. 7, 1069. This application Nov. 24, 1971, Ser. No. 202,009

Claims priority, application Japan, Mar. 15, 1968, 43/ 16,923 Int. Cl. C22c 39/20, 39/14; F01d /14 U.S. Cl. 75-122 18 Claims ABSTRACT OF THE DISCLOSURE A highly corrosion-resistant alloy of the system Cu-Fe, which has both copper-alloy-like characteristics in production techniques and corrosion-resistant properties, and steel-like characteristics in strength and low cost, the alloy consisting of 2-50 weight percent Cu, 5-20 weight percent Ni, 15-35 weight of Mn, and the balance of Fe, with 0.01-15 weight percent Cr or 0.01-5 weight percent Al added thereto.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of Application Ser. No. 805,367 filed on Mar. 7, 1969 for: Cu-Fe System Alloy now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to an alloy of the system Cu-Fe which is very useful as a material for the structural parts of machines or apparatus used for instance in sea water, such as ships propellers.

For these uses, such copper alloys have so far been chosen which exhibit relatively high strength in the order of brass or aluminum bronze. This choice resulted from the doubt whether the application of steel materials, such as so-called stainless steel, would be suitable for use in sea water, because these steels do not have satisfactory corrosion resistance to sea water, which is a non-oxidizing saline solution. In such a solution, stainless steel frequently undergoes corrosion of the pitting type. The materials also have a low corrosion fatique strength with the result that cracking frequently occurs. Copper alloys were therefore mainly used in sea water up to now. However, these alloys have two disadvantages; they are more expensive than ferrous materials, and their strength is inferior than that of those materials. In order to eliminate these drawbacks, it has been considered to use a high strength steel under cathodic protection. However, this means is not always applicable for all the structural parts of machines or apparatus, because in that case a device protecting against corrosion must be additionally provided. Moreover, steels are difiicult to work because of their high meling temperature and their high hardness.

A general object of the present invention is to provide an alloy of the system Cu-Fe that combines the advantages of a copper alloy in the production process and the corrosion resistance, with the advantages of a steel ma terial as to strength and expenses incurred. Therefore, the alloy according to the invention may be produced in a similar technique as copper alloys. The cathodic protection is not required for use of the alloy of the invention in sea water, and its strength is far higher than that of the usual copper alloys. The alloy of the present invention can be used for ships propellers, impellers, water turbines, condenser tubes, condenser tube plates, and the like.

SUMMARY OF THE INVENTION The alloy of the present invention is a copperiron base alloy containing Ni, Mn and Cr. In a simple copper-iron binary alloy, it is impossible to produce a solid solution containing a large quantity of copper, because the solubility of copper in the ferrite phase of iron is low. However, the austenite phase of iron containing a certain amount of Ni and Mn, is capable of dissolving a large quantity of copper. On the other hand, in the case of addition of iron to a pure copper base metal, the a phase of the copper rich side of Cu-Fe alloy, which has the same [face-centered cubic structure as the austenite phase, precipitates iron as a primary crystal at above 2.8 weight percent Fe so that a solid solution cannot be obtained. The copper rich phase of the copper alloy containing Ni and Mn in a certain amount is capable of dissolving a large quantity of iron. That is to say, in a Cu-Fe-Ni-Mn alloy system, solid solutions can be obtained at a proper content of each element, both as the austenite phase of the iron rich region and as the a phase of the copper rich region. Moreover, in order to improve corrosion resistance, CI is added to the Cu-Fe-Ni-Mn alloy. For the same purpose, Al may likewise be added. Therefore the alloy of the present invention contains Cu, Fe, Ni, Mn, Cr and A1 for practical use.

To form the austenite phase by addition of Ni and Mn to Fe, and to satisfactorily dissolve copper in that phase, the addition of 520 weight percent Ni and of 15-35 weight percent Mn is required. The purpose of producing this Cu-Fe-Ni-Mn base alloy is to dissolve Cu in the austenite phase satisfactorily, and to attain good corrosion resistance in non-oxididing aqueous solutions.

The invention is preferably concerned with providing a preferred copper alloy composition of the following in percentages by weight:

(a) from about 26 to about 48% Cu,

(b) from about 8 to about 30% Fe,

(c) from about 15 to about 20% Ni,

(d) from about 18 to about 25% Mn, and (e) from about 2 to about 4% Al.

Further, the invention is also preferably concerned with providing a second preferred. copper alloy compositions having the following in percentages by weight:

(a) from about 20 to about 30% Cu, (b) from about 20 to about 35% Fe, (c) from about 13 to about 20% Ni, (d) from about 15 to about 22% Mn, (e) from about 7 to about 13% Cr, and (i) from about 2 to about 4% Al.

Moreover, the invention is also concerned with providing articles of manufacture composed of the aforesaid two preferred copper alloy compositions. Such articles of manufacture include machine parts exposed to salty water such as propellers, condenser tubes, pipes, impellers and steam turbine parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the alloy according to the invention is shown in Table 1.

TABLE 1 Compositions of Cu-Fe-Ni-Mn-Al alloys and their electric potential (In sea water, at the saturated eclomel electrode potential) Chemical compositions (percent) 1 1 Expected compostitions.

tective coating, the stability of the austenite phase, on mechanical properties, melting behaviour and castability. Addition of more than would raise the melting temperature of the material and injure its castability. Addition of a large amount of Cr to Cu for the purpose of improving the corrosion resistance of Cu, which has not been realized previously because of difiicult problems such as the two phase separation of the liquid phase, is now possible in accordance with the invention.

A second example is shown in Table 2 on the following page. The Cu-Fe-Ni-Mn alloys containing no Cr have better mechanical properties than conventional Cu alloys.

TABLE 2 Mechanical properties of conventional materials and the alloys of the present invention Mechanical properties 2 Chemical compositions (percent) 1 Tensile Fatigue strength Elongation Hardness strenth Materials Cu Fe Al Mo (kg/mm?) (percent) (HB) (kg/1mm N kel luminum bronze 5. 3 9. 4 67-71 15-25 150-180 25 18 2; staiiless steel Bal. 1s 2 52-57 40-60 140-150 30 Sample 1 36 2 70. 5 36. 2 182 30 Sample 2 26 3O 2 70. 2 34. 8 182 Sample 3 44 4 75. 5 21. 2 201 Sample 4 25 2 76.6 36. 4 207 42 Sample 5 30 20 2 85.4 18.0 238 47. 5 Sample 6 30 24 2 72. 4 34. 4 190 Sample 7 26 30 3. 5 83. 8 17. 8 217 Sample 8 22 27 4 80. 8 20. 4 217 Sample 9 20 31 3 70.4 24.5 187 Sample 10 20 4 85. 5 20. 0 230 1 Expected compositions. 9 Castings cooled at the velocity of 5 C./m1n.

As is clear from the table, the potentials of Cu-Fe- Ni-Mn base alloys are -0.2 to O.35 volt in sea water at the saturated calomel electrode potential, and are sufficiently nobler than 0.7 volt of ferrous materials. Thus,

The Cu-Fe-Ni-Mn-Cr-Al alloys with Cr added, as shown in Table 3, have superior mechanical properties, especially, a highly improved corrosion fatigue strength and an excellent corrosion resistance.

TABLE 3 Comparison of the corrosion resistance of the alloys of Example 3 of the present invention and the existing materials Corrosion resistance to sea water 2 Chemical compositions (percent) Maximum Corro- Corrodepth of sion sion pitting rate fatigue Materials Cu Fe Ni Mn Cr Al Mo (nun. (m.p.y.) strength Nickel, aluminum, bronze 80. 4 5. 3 4. 7 0. 2 9. 4 0. 2 2. 3 21 18-8 stainless steel Bal. 1 2 18 1. 7 0. 6 24 Sample 4 30 25 15 15 13 2 0. ()2 34 Sample 5 30 0 15 20 13 2 0. 02

l Expected compositions.

2 Exposure to corrosion is 6 months. Castings are cooled at the velocity of 5 C./min.

3 Cannot be measured.

addition of Cr, which is a powerful element of forming a protective coating, to the Cu-Fe-Ni-Mn base alloy further improves the corrosion resistance of the alloy. A so-called stainless steel produced by addition of Cr to a base alloy having a poor potential, such as steel, undergoes corrosion of the pitting type because of low corrosion resistance of the matrix, causing troubles thereby. Addition of Cr to the Cu-Fe-Ni-Mn base alloy containing a satisfactory quantity of Cu eliminates the incidence of pitting corrosion and makes it possible to obtain desirable corrosion resistant alloy. The content of Cu required for the increase of corrosion resistance of the Cu-Fe- Ni-Mn base alloy is in the range of 2 to weight percent. The purpose of addition of Al to the alloy is to decrease the density of the material and to produce the coating effect of Al which is similar to Cr. However, the addition of Al is limited to at most 5 weight percent, because, otherwise, the formation of the Ni Al phase would increase so that the mechanical properties of the alloy might be injured. The content of Cr, is lirnted to 15% at the u o t a d p ds on he desired effects of pro- The alloys of the present invention can be melted in a low frequency melting furnace for copper alloys, their melting points being 1250 to 1330 C., and can be cast in cement-sand moulds in conventional use even in the case of casting propellers. Besides, there is little difference between the machinability of the alloys of the invention and that of the usual copper alloys, and the cost of the material is one half of the copper alloys. Consequently, the alloys of the present invention are very useful for industrial purposes.

The alloys of the present invention also can be used as materials for machine parts requiring corrosion resistance, such as condenser tubes made by plastic Working, forging and rolling. The alloy may contain not only the usual impurities such as C, Si, P, S and others, but also stabilizing elements of carbides such as Ti, B and Nb. Forming elements of nitrides such as Ti, Zr and V may be added, but the maximum additions of Ti, B, Nb, Zr and V are limited to 0.1 weight percent. Although Mo and Co may be added in view of improving the mechanical properties and the corrosion resistance the maximum additions of Mo and Co are limited to weight percent, in view of the metallographic structures and the material costs. Low melting elements such as Zn, Sn, -Pb, which are present in usual Cu alloys, may also be added, but the maximum additions thereof are up to 3 weight percent.

What is claimed is: 1. Copper-iron alloy composition having the following composition in percentages by weight:

(a) from about 26 to about 48% Cu, (b) from about to about Ni, (c) from about 18 to about Mn, and (d) from about 2 to about 4% Al (e) balance Fe, said Fe being present in an amount of from about 8 to about 2. Copper-iron alloy composition having the following composition in percentages by weight:

(a) from about 20 to about 30% Cu, (b) from about 13 to about 20% Ni, (c) from about 15 to about 22% Mn, (d) from about 7 to about 13% Cr, and (e) from about 2 to about 4% Al (f) balance Fe, said Fe being present in an amount of from about 20 to about Cu. 3. Alloy, according to claim 1, having the composition in percentages by weight:

Cu-48%; Fe-8%; Ni20%; Mn-22%, Al2%. 4. Alloy, according to claim 1, having the composition in percentages by weight:

Cu-44%; Fe-l2%; Ni20%; Mn-22%; Al2%. 5. Alloy, according to claim 1, having the composition in percentages by weight:

Cu-36-%; Fe-20%; Ni20%; Mn-22%; Al2%. 6. Alloy, according to claim 1, having the composition in percentages by weight:

(Eu-26 Fe-30%; Ni20%; Mn-22% Al-2% 7. Alloy, according to claim 2, having the composition in percentages by weight:

Cu-30%; Fe-25%; Ni-15%;

Al2%. 8. Alloy, according to claim 2, having the composition in percentages by Weight:

(Du-30%; Fe-20%; Ni-15%;

9. Alloy, according to claim 2, having the composition in percentages by weight: (Eu-30%; Fe-24%;

Al-2%. 10. Alloy, according to claim 1, having the composition in percentages by Weight:

Cu-48%; Fe-16%; Ni-15%; Mn-18%; Al-3%. 11,. Alloy, according to claim 1, having the composition in percentages by weight:

(Eu-44%; Fe-15%; Ni18%; Mn-20%; Al-3%.

Mn-l5%; (Dr-13%;

Mn-20%; Cr-13%;

12. Alloy, according to claim 1., having the tion in percentages by weight:

Cu-29%; l e-25%; Ni-17%; Mn-25%; Al-4%. 13. Alloy, according to claim 2, having the composition in percentages by weight:

Gil-26%; Fe-30%; Ni-13%; Mn-15%; Cr-12.5%;

Al-3.5%. 14. Alloy, according to claim 21, having the composition in percentages by weight:

Cu-22%; Fe27%; Ni20%;

Al-4%. 15. Alloy, according to claim 2, having the composition in percentages by weight:

Ctr-20%; Fe-31%; Ni-17%;

Al-3%. 1.6. Alloy, according to claim 2, having the composition in percentages by weight:

Cu-20%; Fe-35%; Ni-13%;

Al-4%. 17.. As an article of manufacture, a ship propeller having the composition in percentages by weight:

(a) from about 2% to about 4% Al, (b) from about 26% to about 48% Cu, (c) from about 15% to about 20% Ni, (d) from about 18% to about 25% Mn, and (e) balance Fe, said Fe being present in an amount of from about 8 to about 30%. 18. As an article of manufacture, a ship propeller having the composition in percentages by weight: (a) from about 7% to about 1.3% Cr, (b) from about 2% to about 4 Al, (c) from about 20% to about 30% Cu, (d) from about 13% to about 20% Ni, (e) from about 15% to about 22% Mn, and (f) balance Fe, said Fe being in an amount of from about 20% to about 35% Fe.

composi- Mn-17%; (Ir-10%;

Mir-210%; Cr-9%;

Mn-15%; Cr-13%;

References Cited UNITED STATES PATENTS 1,389,446 8/1921 Hecht et a1. 134

2,184,305 12/1939 Kropf 75-125 3,079,252 2/1963 Webb et al 75-161 FOREIGN PATENTS 120,235 6/ 1946 Australia 75-159 120,236 6/1946 Australia 75-159 CHARLES N. LOVELL, Primary Examiner US. Cl. X.R. 75-134, 153, 159, 161, 162; 416-241 

